Impulsivity Characterization in the Roman High- and Low-Avoidance Rat Strains: Behavioral and Neurochemical Differences

Abstract

The selective breeding of Roman high-(RHA) and low-avoidance (RLA) rats for rapid vs extremely poor acquisition of active avoidance behavior in a shuttle-box has generated two phenotypes with different emotional and motivational profiles. The phenotypic traits of the Roman rat lines/strains (outbred or inbred, respectively) include differences in sensation/novelty seeking, anxiety/fearfulness, stress responsivity, and susceptibility to addictive substances. We designed this study to characterize differences between the inbred RHA-I and RLA-I strains in the impulsivity trait by evaluating different aspects of the multifaceted nature of impulsive behaviors using two different models of impulsivity, the delay-discounting task and five-choice serial reaction time (5-CSRT) task. Previously, rats were evaluated on a schedule-induced polydipsia (SIP) task that has been suggested as a model of obsessive-compulsive disorder. RHA-I rats showed an increased acquisition of the SIP task, higher choice impulsivity in the delay-discounting task, and poor inhibitory control as shown by increased premature responses in the 5-CSRT task. Therefore, RHA-I rats manifested an increased impulsivity phenotype compared with RLA-I rats. Moreover, these differences in impulsivity were associated with basal neurochemical differences in striatum and nucleus accumbens monoamines found between the two strains. These findings characterize the Roman rat strains as a valid model for studying the different aspects of impulsive behavior and for analyzing the mechanisms involved in individual predisposition to impulsivity and its related psychopathologies.

High impulsivity predicting vulnerability to cocaine addiction in rats: some relationship with novelty preference but not novelty reactivity, anxiety or stress

“…Nevertheless, the present findings do show that these two behavioural traits can be dissociated in certain settings. Consistent with this view, Roman high-avoidance rats, which show less anxiety and reduced emotional reactivity to stressful stimuli compared with Roman low-avoidance rats (Escorihuela et al 1999), are reported to be more impulsive on both the 5-CSRTT and the delay-discounting task (Moreno et al 2010).…”

Schedule-induced polydipsia as a model of compulsive behavior: neuropharmacological and neuroendocrine bases

“…Moreover, selective breeding for Roman high-(RHA) and low-avoidance (RLA) rats for rapid vs. extremely poor acquisition of active avoidance behavior in a shuttle box resulted in two phenotypes that included differences in sensation/novelty seeking, anxiety/fearfulness, stress responsivity, and susceptibility to addictive drugs (Driscoll et al 1998;Escorihuela et al 1997Escorihuela et al , 1999Fattore et al 2009). They also showed differences in two models of impulsivity, impulsive choice in delay discounting task and poor inhibitory control in 5-CSRTT, and in compulsivity in SIP acquisition and performance, with RHA manifesting impulsive-compulsive behavior (Moreno et al 2010). The characteristics that have been selected or bred in these different groups of rat strains did not point towards a specific common trait among them that could link with compulsive drinking.…”

“…This excessive drinking, induced in food-deprived animals (80-85% from free feeding) and known as SIP, has been proposed as a prototype of adjunctive behavior and is unrelated to normal thirst or homeostatic needs, generally following an inverted-U-shaped pattern occurring immediately after the delivery of food (Falk 1961(Falk , 1971. Although different factors, such as the state of food deprivation or the interfood interval length reproduced by different fixed time (FT) or fixed interval (FI) schedules, influence the acquisition and expression of adjunctive drinking in SIP (Falk 1966a(Falk , 1971Flores and Pellón 1995;Flory 1971;Killeen 1970;López-Crespo et al 2004), data from our laboratory have shown that the optimal FT interval for inducing a high rate of drinking behavior is FT-30s (Cardona et al 2006) and FT-60s (López-Grancha et al 2006aMoreno et al 2010). The main variables measured during SIP are: (a) total amount of water (milliliters) removed from the bottle, (b) total number of licks, and (c) and total number of nose pokes in the food magazine.…”

“…Not all animals submitted to the same conditions develop adjunctive drinking, and even those animals that show SIP acquisition exhibit considerable variability in the amount of water consumed (Dantzer et al 1988a, b;López-Grancha et al 2006aValenstein 1984, 1985;Mittleman et al 1988a, b;Moreno et al 2010;Pellón et al 2011;Tazi et al 1988). In fact, there are considerable and consistent individual differences observed in the rate of drinking after 15-20 sessions in SIP which can often justify the formation of two groups of rats, one with high or excessive drinking and a second group with low drinking or no SIP acquisition.…”

“…Pharmacological studies have implicated 5-HT receptors in SIP behavior (Martin et al 1998(Martin et al , 2002Rosenzweig-Lipson et al 2007). Indeed, SIP compulsive drinking rats (HD) have been characterized by their altered baseline levels of 5-HT activity (Moreno et al 2010), and increased perseverative-compulsive responses to extinction condition and increased sensitivity to D-amphetamine effects in prematureimpulsive responses in the 5-CSRT task . Moreover, these findings in HD and those related to different rat strains that also have showed compulsive drinking in SIP suggest that the lack of inhibitory control might be the main characteristic in this response, as occurs in the human compulsive endophenotype.…”